Unlike invasive blood pressure measurement, non-invasive blood pressure measurement is an indirect method of measuring the blood pressure in an artery of the human body. Currently, there are two categories of non-invasive blood pressure measurement methods.
One method is the auscultatory method (from the Latin word for “listening”), which is the predominant method of clinical measurement due to its accuracy. According to the auscultatory method, an inflatable cuff of a sphygmomanometer is used to apply a changing pressure on an artery to restrict blood flow in the artery. The cuff is first inflated until the artery is completely occluded and then deflated until the artery is open again. The pressure values at the moment of occlusion and at the moment of reopening are commonly called SBP-I (SBP during inflation) and SBP-D (SBP during deflation), respectively. Clinicians manually detect the moment of occlusion and the moment of reopening of the artery by listening with a stethoscope or a Doppler probe and read the SBP values from the sphygmomanometer. The clinicians should have no hearing deficit and are required to highly focus on the devices during the whole measuring procedure. Consequently, when using the auscultatory method to measure SBP, the clinicians might easily start to feel tired, as a result of which the accuracy of the detected moments of occlusion and reopening of the artery is impacted accordingly.
The other method is the oscillometric method. Existing automatic blood pressure measuring devices are all based on the oscillometric method. Clinicians enjoy the convenience brought by the oscillometric method. However, in comparison with the auscultatory method, the oscillometric method is relatively inaccurate, because the measurements are calculated based on statistics without respect to individuals.
Thus, existing blood pressure measurement methods are either inconvenient to use or inaccurate.